Garnet: The State Mineral of Connecticut

In 1977, the Connecticut General Assembly designated the mineral garnet, variety almandine, as the state mineral. The garnet “group” of minerals is well known from many localities around the state. Both ornamental and functional, garnet is readily identified by its small granular crystals, most often seen in a deep reddish brown color.

A very common constituent of our rocks, garnets of several colors and varieties are found in many localities around Connecticut. Some of these include Roxbury, Redding and Colchester.

Garnets are a common constituent of the igneous rock pegmatite, and of coarse granite and granite gneiss. Garnets are also frequently found in mica schist, a common metamorphic rock. One can also find tiny garnets in beach sand and in sandstone deposits. Color can range from colorless through red, cinnamon and yellow, to green, brown and black. The most commonly found garnets in Connecticut are red, reddish brown, with darker colors to black.

Garnets are called a “group” because similar minerals of different chemical composition have the same crystallographic structure. The variety almandine is an iron aluminum garnet. Other varieties found in the state include pyrope, magnesium aluminum; grossular, calcium aluminum; spessartine, manganese aluminum, and andradite, calcium iron.

Transparent garnets of good color can be cut as gemstones, but it is rare to find garnets of that quality in Connecticut. Most commonly, rough garnet is used as an abrasive, as in sandpaper and emery boards.

Courtesy of the Connecticut Society of Civil Engineers Section of the American Society of Civil Engineers. Used by permission. These facsimile PDF versions are provided for research and personal use only. Any other use is prohibited. Contact the CSCE for more information.

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